There are two main types of shuttlecocks, those having a flared skirt made of feathers and those having a flared skirt made of plastic material. Feather shuttlecocks have a cap usually made of cork, the inner skirt being the stems or quills of the feathers and the outer skirt being made up of minor stems or the quill extensions which spread into the vanes. In the best feather shuttlecocks, the flared skirts are made of goose feathers which overlap in the outer skirt. Such shuttlecocks have the following desirable characteristics: the turnover is good; the whole shuttlecock is rigid; it rotates in flight and the outer skirt is very light; when struck severely, there is a resounding `crack`, a noise pleasing to the player; the inner skirt does not collapse and the shuttlecock decelerates rapidly. Such shuttlecocks have two main disadvantages, they are expensive and, if mis-hit, a stem may break and the flight becomes irregular so that the shuttlecock has to be discarded sometimes after only one or two minutes play.
In a plastic shuttlecock, the flared skirt has stems in the inner skirt (replacing quills in the feather); the stems become minor stems in the outer skirt and, to replace the vane in the feather, may be connected by a series of ribs in turn connected by a plurality of intermediate stems; the design varies. Cheaper models are made of a material such as polyethylene whilst the more expensive models are made of a material such as polyamide.
In models made according to the prior art, the deeper, stiffer and more numerous the stems, the more quickly the skirt recovers after collapsing when struck severely but the poorer the turnover. The turnover can be improved by reducing the number and/or cross-sectional area of stems, minor stems, ribs and intermediate stems. Spinning can be induced by inclining the stems and/or indenting parts of the outer skirt. The more the skirt is filled in by stems, minor stems, ribs and intermediate stems the better the `crack` and visibility but the worse the turnover. Manufacture is a matter of comprise between stiffness, `crack` visibility and turnover. Such shuttlecocks are known from GB-A-887172, GB-A-907700, GB-A-908684, GB-A-1046708 and, in particular, GB-A-949110. The shuttlecock known from GB-A-949110 has an upper skirt made of natural or artificial quills and a lower skirt made at least in part of a cellular plastic material. In one embodiment, the lower skirt is made from a solid as distinct from cellular material coated with a surface layer of cellular plastic material. In another embodiment, the lower skirt is made of a cellular plastic material.
Because of the rigidity of a new feather shuttlecock, when it is struck severely, the cap and feathers move together so that when the shuttlecock is in good condition collapsing is negligible but when a plastic shuttlecock, even a new one, is struck severely it can be shown by high speed photography that the skirt collapses until it is almost flat as shown in FIG. 1; the collapse is prolonged because the skirt is not strong enough to return to a substantially circular shape as it passes through the air with the result that when struck severely in a `lob` the `length`, as dictated by the laws of badminton, may become unpredictable.
Technical Problem to be Overcome
The technical problem to be overcome in both the feather and the plastic shuttlecock is to provide a gradual support for the stems so that they are less likely to break when mis-hit and, in the plastic shuttlecock,
1) to support the stems to prevent the collapse of the skirt or make the recovery so quick as to make the collapse unimportant; PA1 2) to fill in the spaces between the stems sufficiently to make the `crack`; PA1 3) to improve visibility and turnover.